X.25

protocol, standard An ITU-T standard protocol suite

for the DTE-DCE interface in a packet-switched network,

approved by ISO. X.25 defines standard physical layer,

data link layer and network layers (layers 1 through 3).

It was developed to describe how data passes into and out of

public data communications networks. X.25 networks are in use

throughout the world.

Document: ISO 8208.

Several other ITU-T recommendations are relevant to packetswitching: X.3, X.28, X.29, X.75.

(1996-08-10)